1. Field of the Invention
The present invention relates to a partition wall arrangement for an exhaust gas pipe for separating the interior of the pipe into a pair of longitudinally extending passages, and in particular to a partition wall arrangement for a pair of exhaust gas pipes which are coupled to each other by a flexible coupling such as a spherical coupling.
2. Description of the Related Art
An exhaust gas pipe at the converging end of an exhaust manifold for a multi cylinder engine and an exhaust pipe immediately downstream of the exhaust manifold are sometimes each separated into a pair of longitudinal passages each having a semicircular cross section by a corresponding partition wall for the purpose of avoiding exhaust gas interferences. Such a partition wall is exposed to the high temperature of the exhaust gas, and is therefore required to be able to withstand the resulting thermal stress (see Japanese patent laid-open publication No. 9-4451).
Also, in order to insulate the vibrations of the engine from being transmitted from the converging end of the exhaust manifold to the exhaust gas pipe in the downstream which is fixedly attached to the vehicle body, a spherical coupling is sometimes interposed between the converging end of the exhaust manifold and the exhaust gas pipe. The engine is typically mounted on rubber mounts to accommodate the vibratory motion of the engine. In such a case, the opposing edges of the partition walls of the converging end of the exhaust manifold and the exhaust gas pipe are spaced from each other so as to accommodate the relative flexing movement of the two parts that are joined by the spherical coupling. Therefore, a small gap is created between the opposing edges of the partition walls.
When the edges of the two partition walls oppose each other, and exhaust gas flows along the partition walls at high speed, the partition wall on the downstream side may vibrate as a membrane. This tendency is even more pronounced when the exhaust gas flow contains a pulsating component. This causes a repeated stress to the partition wall, and could severely impair the durability of the partition wall when combined with the effect of the high temperature of the exhaust gas.
In view of such problems of the prior art, a primary object of the present invention is to provide a partition wall arrangement for exhaust gas devices having an improved durability through elimination of membrane vibrations.
A second object of the present invention is to provide a partition wall arrangement for exhaust gas devices which is relatively free from the adverse influences of the heat of the exhaust gas.
A third object of the present invention is to provide a highly durable partition wall arrangement which is easy and economical to manufacture.
According to the present invention, such objects can be accomplished by providing a partition wall arrangement for an exhaust gas pipe section including a partition wall separating the pipe section into two longitudinal passages, the partition wall comprising: a main plate member extending diametrically across an inner circumferential surface of the pipe section and longitudinally over a certain length of the pipe section so as to define a pair of longitudinal passages inside the pipe section each having a semi-circular cross section; and a reinforcing plate member placed over and attached to a major surface of the partition wall member preferentially in a part adjacent to the upstream edge of the main plate member.
The reinforcing member is effective in reinforcing the partition wall, and raises the resonant frequency of the partition wall. This prevents the membrane vibration of the partition wall even when the exhaust gas flow contains pulsating components, and improves the durability of the partition wall. Because the reinforcement of the upstream edge of the reinforcing plate member is particularly effective in controlling the vibration, the reinforcing member may include a relatively broad upstream portion and a relatively narrow downstream portion so as to minimize the increase in the overall weight of the arrangement. For an added reinforcement, a second reinforcing member may be placed over and attached to the other major surface of the partition wall member preferentially over a part adjacent to the upstream edge of the pipe section.
Because the upstream edge of the partition wall is most exposed to the influence of the heat of the exhaust gas, it is preferable to provide an edge cover which is wrapped around upstream end edges of the reinforcing member and the main plate member. The edge cover may consist of a flange or an extension of the reinforcing member. Such an edge cover is also beneficial in reinforcing the edge portion of the partition wall, and in controlling the size of the gap between the opposing edges of the partition walls of two pipe sections which are connected to each other. Reducing the size of the gap contributes to the increase in the engine output and reducing the noises due to the interferences of the pressure pulsations between the different cylinders of the engine.